Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions - Determination to make a minor amendment to Part 3 of Schedule 1 of the Threatened Species Conservation Act

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Determination to make a minor amendment to Part 3 of Schedule 1 (Endangered ecological communities) of the Act by inserting the Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions (as described in the determination of the Scientific Committee under Division 5 Part 2) and as a consequence to omit reference to the Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions (as described in the final determination to list the ecological community) which was published on pages 1265 to 1268 in the NSW Government Gazette No. 42 dated 8 April 2005. Minor amendments to the Schedules are provided for by Division 5 of Part 2 of the Act.

The Scientific Committee is of the opinion that the amendment is necessary or desirable to correct minor errors or omissions in the Determination in relation to the Thackway and Cresswell (1995) reference.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions is the name given to the ecological community that occurs north of Bourke between the Culgoa and Warrego Rivers on soft red earths and heavy grey clays (Isbell 1962) on level to slightly undulating plains. The community is characterised by the following assemblage of species:

2. The total species list of the community is considerably larger than that given above, with many species present in only one or two sites or in low abundance. The species composition of a site will be influenced by the size of the site, recent rainfall or drought condition and by its disturbance (including fire) history. At any one time, above ground individuals of some species may be absent, but the species may be represented below ground in the soil seed banks or as dormant structures such as bulbs, corms, rhizomes, rootstocks or lignotubers. The list of species given above is of vascular plant species, the community also includes micro-organisms, fungi, cryptogamic plants and a diverse fauna, both vertebrate and invertebrate. These components of the community are poorly documented.

3. The structure of this ecological community ranges from woodland to shrubland and scrub depending on local conditions. The canopy is dominated by either Brigalow (Acacia harpophylla) or Gidgee ( Acacia cambagei) with the other species being co-dominant or part of the shrub layer, depending on site disturbance. Large areas of the ecological community have been disturbed by previous clearing and thinning activities and may now have a greater proportion of Gidgee present, such as those mapped as Rung Plain by Wade (1992) and some of the areas mapped as Fallen Treated Timber by the Northern Floodplains Regional Planning Committee (2004a, 2004b). These areas are considered part of Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions. Both understorey and overstorey vegetation would, under appropriate management, respond to natural regeneration where the natural soil and associated seed bank are still intact.

4. Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions includes the ‘Brigalow, Brigalow-Gidgee, Drainage and Rung Plains’ Types of Wade (1992) and these vegetation types are almost exclusively found on the ‘Myurna, Ellerslie and Ledknapper’ Land Systems of Walker (1981). Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions includes all of the ‘Brigalow Vegetation Community’ and part of the ‘Gidgee Vegetation Community’ mapped by the Northern Floodplains Regional Planning Committee (2004a, 2004b). The ‘Gidgee’ Type of Wade (1992) and the ‘Gidgee Vegetation Community’ mapped within the Darling Riverine Plains Bioregion does not form part of this ecological community (Northern Floodplains Regional Planning Committee 2004a). Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions is part of Pickard and Norris’s (1994) broader map units, ‘Acacia cambagei low open-forest’ (map unit 16) and ‘ Acacia harpophylla low open-forest’ (map unit 17) and belongs to the ‘Brigalow Clay Plain Woodland’ vegetation class of Keith (2002, 2004).

5. Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions has been recorded from parts of the local government areas of Bourke and Brewarrina, but may occur elsewhere in the Bioregions. Bioregions are defined in Thackway and Cresswell (1995).

6. Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions community has been extensively modified with at least 79% of the estimated original 190,000 ha cleared or thinned (Wade 1992). Mapping based on satellite imagery found that about 33% of the community was classified as ‘Fallen Treated Timber’ (Northern Floodplains Regional Planning Committee (2004a, 2004b). Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions is threatened by clearing and thinning, burning, grazing by stock and feral animals (Northern Floodplains Regional Planning Committee (2004a, 2004b). Clearing of native vegetation and Competition and habitat degradation by Feral Goats, Capra hircus are listed as Key Threatening Processes

7. Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions has not been recorded from any conservation reserves.

8. In view of the above the Scientific Committee is of the opinion that Brigalow-Gidgee woodland/shrubland in the Mulga Lands and Darling Riverine Plains Bioregions is likely to become extinct in nature in New South Wales unless the

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 02/12/11
Exhibition period: 02/12/11 – 03/02/12

References:

Isbell RF (1962) ‘Soils and vegetation of the brigalow lands, Eastern Australia.’ CSIRO, Soils and Land Use Series No 43, Canberra.

Keith DA (2002) A compilation map of native vegetation for New South Wales. NSW Biodiversity Strategy. NSW National Parks and Wildlife Service, Sydney.

Keith DA (2004) ‘Ocean shores to desert dunes: the native vegetation of New South Wales and the ACT’.(NSW Department of Environment and Conservation: Sydney).

Northern Floodplains Regional Planning Committee (2004a). ‘Vegetation Communities of the Northern Floodplains Western New South Wales Book 2: Brewarrina Shire.’ Northern Floodplains Regional Planning Committee, Walgett NSW.

Northern Floodplains Regional Planning Committee (2004b). ‘Vegetation Communities of the Northern Floodplains Western New South Wales Book 3: North Eastern Section of Bourke Shire.’  Northern Floodplains Regional Planning Committee, Walgett NSW.

Pickard J, Norris EH (1994) The natural vegetation of north-western New South Wales: notes to accompany the 1:1 000 000 vegetation map sheet. Cunninghamia 3, 423-464.

Thackway R, Cresswell ID (1995) An interim biogeographic regionalisation for Australia: a framework for setting priorities in the National Reserves System Cooperative Program. (Version 4.0. Australian Nature Conservation Agency: Canberra.)

Wade T (1992) ‘The brigalow outlier: a resource inventory of the brigalow vegetation communities west of the Culgoa River.’ Dept of Conservation and Land Management, Dubbo.

Walker PJ (1991) ‘Land Systems of Western New South Wales’ Soil Conservation Service of NSW, Technical Report No. 25, Dubbo.